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Anat 262 > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

Largest organelle

A

Nucleus

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2
Q

Organization of the nucleus starting from the cytoplasm?

A
  1. Nuclear envelope
  2. Nuclear lamina
  3. Nuclear interior
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3
Q

Nuclear envelope structure?

A

Outer nuclear membrane
Perinuclear space
Inner nuclear membrane

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4
Q

T/F: Inner/outer nuclear membranes differ in the proteins they carry

A

True

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5
Q

Nuclear pore complex?

A

Found at the junction of the inner and outer nuclear membranes, these mediate trafficking of most material in/out of the nucleus

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6
Q

Components of the nuclear interior?

A

Nucleolus
Chromatin
Nuclear bodies
Nuclear matrix

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7
Q

What is the nucleolus?

A

Complex compartment formed by phase separation

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8
Q

What are nuclear bodies?

A

Large variety of compartments within the nucleoplasm that don’t have a membrane and form by phase separation
-Involved in splicing and DNA repair

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9
Q

Nuclear matrix?

A

Filamentous system within the nucleus

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10
Q

T/F: Outer nuclear membrane is continuous with the ER?

A

True

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11
Q

T/F: perinuclear space is continuous with the ER lumen?

A

True

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12
Q

Heterochromatin vs Euchromatin in the nucleus?

A

Heterochromatin is close to the nuclear envelope whereas euchromatin is in the middle of the nucleus

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13
Q

Does the nucleolus have a membrane?

A

No

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14
Q

How many nucleoli do mammalian cells have?

A

2-3

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15
Q

Functions of the nucleoli?(9)

A
  1. Produce/process 47S rRNA
  2. Assemble ribosomal subunits(both)
  3. Assemble signal recognition particle
  4. Regulate aptosis (cell death)
  5. Regulate progression through the cell cycle
  6. Control the function of p53
  7. Control telomerase function
  8. Regulate stress response
  9. Viruses replicate in the nucleoli
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16
Q

Compartments of the nucleolus formed by phase separation?

A

1.Granular compartment
2. Dense fibrillar component embedded in GC
3. Fibrillar component embedded in DFC(RNA pol 1 for 47S rRNA)

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17
Q

How is 47S rRNA precursor synthesized?

A
  1. RNA-pol I which generates the 47S rRNA precursor is found in the fibrillar component of the nucleoli
  2. RNA pol I trascribes the RNA precursor 47S at the border of the FC and DFC
  3. This transcript then moves through the nucleolus where it is processed and proteins are added
  4. Now we have a ribosomal subunit that matures outside the nucleolus
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18
Q

Where is nucleophosmin(NPM) found?

A

Granular component of the nucleolus

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19
Q

Properties of phase separation?

A

Drop like

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20
Q

How to test for phase separation?

A
  1. Place FBL and NPM in a test tube and mix them
  2. They generate droplets in the tube(LLPS occurs)
  3. These droplets are not uniform some compartments contain NPM and other FBL (this proves they tend to separate from each other)
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21
Q

What is FBL(fibrillation)?

A

Protein found in the dense fibrillar component of the nucleolus

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22
Q

Four types of rRNA?

A
  1. 28S
  2. 5.8S
  3. 5S
  4. 18S
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23
Q

What rRNA make up the 47S precursor?

A

5.8S, 28S and 18S

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24
Q

How many copies of rRNA genes do we have?

A

10

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25
Q

Nucleolar Organizers?

A

Contain active rRNA genes, the transcripts will then form in the nucleoli

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26
Q

Processing the rRNA?

A

Involves cutting pre rRNA into the 28S, 18S and 5.8S

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27
Q

Where is 5S rRNA made?

A

Nucleoplasm

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28
Q

Why don’t we do protein translation in the nucleus?

A
  1. Don’t want to make proteins that chew up DNA
  2. If we have huge complex that we need to assemble for the cytoplasm we may not be able to get it across the NPC
  3. In the nucleus we have unspliced and different intermediates of mRNA whereas in the cytoplasm we have properly splice mRNA , if we use unspliced mRNA this will make useless protein(could be potentially toxic)
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29
Q

Why do patients with cancer have large nucleoli?

A

They need a lot of rRNA to make a lot of ribosomes and protein which help the cancer cells to divide

30
Q

NPC mass?

31
Q

Structure of the NPC

A

Has 8 fold symmetry
has a central gated channel in the middle

32
Q

Role of NPC

A

Active transport and diffusion

33
Q

Size of molecules that can diffuse through NPC?

A

smaller than 40kDa

34
Q

Size of molecules transported through NPC via active diffusion?

A

Larger than 40kDa

35
Q

Proteins in the NPC

A

-8 fold symmetry each slice has a set of different protein
-Each slice has 35 different proteins but these 35 different proteins can come various in copies of 1, 2, 3, 4, 5, etc. in each slice
-Each NPC has about 100 proteins

36
Q

Nucleoporins

A

-Proteins in the NPC
-Can come with repeats or without
-NUP and then a number

37
Q

FXF repeats nucleoporins?

A

Have several copies of this repeat sequence and are able to undergo phase separation
Involved in transport in/out of the nucleus

38
Q

GFLF repeat nucleoporins?

A

-RNA transport

39
Q

No repeat nucleoporins?

A

-Anchor the NPC to the membrane

40
Q

Nuclear Lamina

A

-Under the inner nuclear membrane
-Composed of lamina which are intermediate filaments

41
Q

Filamentous vs non filamentous nuclear lamina?

A

Filamentous lamins underly the nuclear membrane
Non-filamentous are within the nucleus

42
Q

Nuclear Lamina connection?

A

Connects to the inner nuclear membrane and with the chromatin

43
Q

LBR (nuclear envelope protein)

A

Protein in the inner nuclear membrane that contacts the nuclear lamina which contacts chromatin
-Multiple transmembrane domains
-Lamin binding domain and chromatin binding domain

44
Q

LAP2

A

Proteins in the inner nuclear membrane that contacts both the lamina and the chromatic
-One transmembrane domain, laminin binding domain, chromatin binding domain

45
Q

Two proteins that allow nucleus and cytoplasm to communicate?

A

SUN and KASH

46
Q

SUN Proteins?

A

In the inner nuclear membrane, have large domains in the perinuclear space that interact with KASH

47
Q

KASH proteins

A

In the outer nuclear membrane
Have large domains in the cytoplasm

48
Q

LINC complexes?

A

Contact between inner/outer nuclear membrane proteins
Links the nucelus and cytoplasm

49
Q

Do KASH proteins interact with proteins in the cytoplasm?

A

Yes, they interact with actin/microtubules

50
Q

Why connect the nucleoskeleton and cytoskeleton?

A

-Makes it possible to deform the nucleus to move large complexes across the tissue
-Cell migration relies on changing the shape of a cell or shape of the nucleus, the communication between the nucleoplasm and the cytoskeleton(which is organizing the shape of the nucleus) allows the cell to deform and allow for migration

51
Q

How are nuclear lamins different from other intermediate filaments?

A

Nuclear localization

52
Q

Lamin formation

A
  1. Lamin monomers associate into dimers (both heads facing same way)
  2. Head-to-tail association occurs between dimers forming polymers
  3. Polymers associate into higher structures
53
Q

What happens to nuclear lamins during mitosis when they need to be disassembled?

A

Both the head and tail domains of the higher structures are phosphorylated which causes the filaments to fall apart. At the end of mitosis we dephosphorylated

54
Q

Two families of lamins?

A

LaminA : Soluble in mitosis
LaminB: Remain associated with membranes during mitosis

55
Q

How many Lamin A genes are there?

A

One, to get different type sof lamin A we splice them differently

56
Q

How lamin B geness are there ?

A

2 (LMNB1, LMNB2)

57
Q

Expression of lamin A?

A

Controlled by differentiation , primarily found in differentiated cells

58
Q

Where are lamin B found?

A

Associated with membranes since they have modified C-terminus

59
Q

Mature Lamin A

A

Long C-terminus and at the end a CaaX motif
-Two cleavage sites

60
Q

Lamin C

A

-Splice variant of lamin A gene
-No cleavage sites or CaaX motif

61
Q

Lamin B

A

-Always has CaaX at the C-terminus

62
Q

Farnesyl Moieties?

A

-Three copies of Isoprenyl that are covalently linked make up the farnesyl moiety
-This moiety is put on the cysteine which is sitting at the C-terminus(CaaX)
-C amino acid becomes modified with the farnesyl

63
Q

Prupose of modifying the C-terminal and then cleaving it off?

A

Use this complex processing scheme to have the lamin in various locations where it may associate/contribute to different functions. Some of these functions probably have something to do with things going on in the nuclear membrane.

64
Q

A-type Lamin binding partners?

A

-Nuclear architecture(proteins of inner nuclear membrane)
-Histones
-Gene regulation
-Signaling

65
Q

Would a lamin A/C knockout mous be alive?

A

Yes, lamin A functions can be compensated by using lamin B

66
Q

T/F: mutant lamin A can be worse than knockout?

67
Q

Hutchinson Gilford Progeria

A

Mutation in the C-terminus of lamin A creates progerin which retains hydrophobic moiety at the C-terminus

68
Q

What is Hutchinson Progeria?

A

Patients prematurely age/die

69
Q

How can lamin A mutations alter different cell types?

A
  1. Lamin A mutationsaffect mechanical properties of the nucleus
  2. Lamin A plays a role in gene expression and can modulate expression of certain genes
70
Q

How can heart cells be affected by LMNA mutations?

A

Lamina supports the structure/organization of the nucleus when the heart is constantly contracting and the lamin a is weak these cells are prone to be damaged or even die

Anat 262 (8 decks)

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